We have previously shown that different interferons (IFNs) are produced by lymphocytes and by fibroblasts as a consequence of S. typhimurium challenge. We have recently demonstrated that tumor necrosis factor (TNF) is present in ligated known about the production of these cytokines in the intestinal tract or in gut associated lymphoid tissue in response to intestinal infection by Salmonella. The role these cytokines play in the pathology associated with enteric bacterial infections is also uncharacterized. The overall goals of this proposal are to: 1) determine if TNF and/or IFN's are produced in vivo in the gastrointestinal tract and/or gut-associated lymphoid tissue in mice challenged with S. typhimurium; 2) characterize the cells present in the gastrointestinal tract and/or gut-associated lymphoid tissue which are producing TNF and/or IFNs following in vivo challenge with S. typhimurium and 3) to determine the role these cytokines play in the pathology associated with S. typhimurium infection of the gastrointestinal tract. TNF and/or IFN production will be assessed following S. typhimurium challenge of ligated intestinal segments or following oral challenge. Cytokine detection will be by bioassay, by molecular biological techniques, and by immunofluorescence in cells and/or tissue sections of gastrointestinal tract. Using cDNA for TNF and IFNs, or specific oligonucleotide primers, we will quantitate specific mRNA present in different tissues and/or isolated cells by Northern analysis or polymerase chain reaction using the MAPPing technique. Tissue sites for TNF and IFN production in vivo will be determine by in situ hybridization on frozen sections of gastrointestinal tissue and on cytospins of different cell populations using 35S-labeled oligonucleotides. Cells producing TNF and/or IFNs will be characterized by in situ hybridization combined with immunocytochemistry. To assess the role that TNF and/or IFNs play in the pathology of these infections, we will determine if antibody to these cytokines alter the histological profile in gastrointestinal tissue of challenged mice. Results from experiments proposed in this application will contribute to our understanding of the role TNF and IFNs play in the pathophysiology of Salmonella infections of the intestinal tract.